The subject invention is directed toward the art of heating apparatus and, more particularly, to a vent or stack damper control system for a combustion-type heating apparatus.
The invention is particularly suited for use on gas-fired water heaters and will be described with reference thereto; however, the invention is capable of broader application and could be used on many different types of fluid fuel-fired furnaces, boilers and similar heating devices.
The typical domestic hot water heater comprises a vertically-extending tank with a central vent tube positioned axially thereof. A gas burner is positioned beneath the tank and is controlled by a thermostatic valve responsive to the temperature of the water within the tank. The water within the tank is, of course, heated by the hot combustion products impinging against the bottom of the tank and traveling through the vent tube. Generally, the exit end of the vent tube is connected through a draft hood with a chimney or stack to convey the combustion products to a location exterior of the building.
The general arrangement described above is in widespread use. One of the major disadvantages is, however, a comparatively low, overall thermal efficiency. For example, during those periods when the burner is not firing, natural thermosyphonic action induces a continual flow of air through the vent tube and up the stack. This causes thermal losses in terms of loss of heated air from the building and cooling of the heated water in the tank. The natural cooling of the heated water causes the burner to be cycled on-and-off even during periods when no heated water is being used.
Various approaches for overcoming the noted losses have been proposed in the prior art. For example, see the following U.S. Pat. Nos.:
Allman, 1,336,937; PA1 Stinson, 1,959,970; PA1 Gilliland, 2,130,491; PA1 Firehammer, 2,179,120; PA1 Woods, 2,218,061; PA1 Stringer, 2,224,705; PA1 Viola, 2,557,210; PA1 Hodgins, 3,010,451.
Generally, the systems shown in the noted patents are unsatisfactory for at least one of several reasons. That is, the systems are either complex, cumbersome, and expensive and/or they require an electrical supply. In addition, the prior systems generally do not provide any means for preventing losses due to heated building air entering the draft hood and going up the chimney.
Because of the problems and disadvantages of the prior systems, they have generally not been suitable for commercial applications either as original equipment or as retrofit units for incorporation in existing equipment.